Fuse link



L. C. HART May 7, 1940'.

FUSE LINK Filed oct. 31, 195e INVENTOR. 5575/? CT #HRT BY fa-L //wf/f ATTORNEYS Patented May 7, 1940 f FUSE LINK Lester C. Hart, Cleveland, hio, assignor to Hi- Voltage Equipment Company, Cleveland, Ohio,

a corporation of Pennsylvania lApplication October 31, 1938, Serial No. ,237,843

s oiaims. (o1. 20o-1135 AThis invention relates to fuses, and more particularly toa fuse link for use in the explosion or` expulsion type of fuse, such as that disclosed in my prior Patent 1,605,543, dated November 2, 1926. 1 -v Practical experience with the type of fuse link shown in my aforesaid prior patent'has shown thatthe use of a relatively long infusible conductor with a relatively short fusible section at one `end thereoigis objectionable, under some conditions, because of the liability of thelong inusible conductor, when expelled, to fall where it will bridge between a conductor and ground or short-circuit apair of conductors. Another objectionable feature of a long infusible conductor is that attendants are liable to be injured by it when it is expelled from the fuse tube.

Itis one of the objects of the presentinvention to provide a fuse link that is especially adapted for the type of fuse mentioned above and will be expelled from the fuse tube in relatively short sections or broken up so that there will be less liability oi injury to attendants as weil as less liability to short-circuit or ground other conductors. A further advantage is that,A because the fuse link is expelled in relatively short sections,` it is possible to locate the fuse closer to other apparatus and thus reduce the cost of installation.

In the accompanying drawing I have illustrated a fuse link embodying my invention. This fuse link comprises a plurality of conductor sections lil, II and I2 which are preferably made of copper cable so as to be flexible and have the requisite current-carrying capacity with a minimum size and weight. The sections IFJ and Il are `joined together by a fusible section or joint I3 which is preferably of tubular form, so as to permit the ends of the sections Iii and II to be inserted therein and soldered thereto. In a similar manner the conductor sections II and I2 are connected together by a fusible section orv joint I4. To the end of the section I2 there is connected a section I 5 of fusible wire which is accurately calibrated to be fused by a current of predetermined amperage in a predetermined time. The connection between the sections I2 and l5 may be by means of a sleeve I5 of good conducting material into which the ends` of the sections i2 and I5 are inserted and then soldered.

A connecting terminal I'I is soldered to the end of the fusible section I5 and, from the drawing, it will be seen that all of the sections referred to are connected together in series so as to form a continuous wire that is adapted for use in the tube of a fuse such as that disclosed in my prior Patent 1,695,543. In making up the fuse link, as described, the conductor sections II and iii are of such length that `when the wire is assembled in the fuse all of 'the fusible sections, such as the sleeves iii and I4 'and' the section I5, willbe within the tube oi the fuse, and it will be understood that while I have iilustrated a fuse link comprisingT the three conductor sections It,

H and Ii, a larger number oi these conductor sections may be used, if desired, by making them shorter and correspondingly increasing the number of the fusible sleeves'` I3 and It.

In making a fuse' link for use in the type of fuse iliustrated in my prior Patent 1,605,543, it is desirable to have the calibrated fusiblesection, such as thefsection I5, locatedatA the end of the wire-so that it will be positioned at the closed end of the fuse tube. This fusible section I is so calibrated as to be fused by a current ofl the amperage representing the rated capacity ofthe fuse,` and the fusible sections ifi and M are so calibrated that for any given current they will fuse after the fusible section E5. This may be insured by so proportioning the sleeves i3 and I4 that they will require a somewhat 'largerr` current to fuse them than that required by the fusible section I5, or the metal of which the sleeves I3 and Id are made may require, for'any given current, a somewhat longer time to fuse than the fusible section I5. In any case, however, the sectionsl I3, I4 and. I5 should be so calibrated that the section I 5 will always fuse in advance of the sections i3 and I 4.

In certain types of fuses lin which my improved fuse link is adapted tofbe used as, for example, that disclosed in my copending application Serial `No. 237,842, led October 31, 1938, it is' under a.

constant tension. Fuses are sometimes subjected to momentary overloads which would tend tor soften and thus weaken the tensile strength "of the fusible section i5. If such overloads are not dangerous to the circuit or apparatus that is protected by the fuse it is desirable that the fusible section I5 should not be broken by the tension on the fuse link, when it is so momentarily softened and weakened. In order to avoid breaking the fusible section i5 under such circumstances I vprovide a reenforcement which consists of a relatively ne wire I8 of material of high tensile strength, such as stainlesssteel. One end of this wire is soldered or otherwise secured to the sleeve E6, and the other end to the terminal il so that it bridges the space occupied by the fusible section I 5 and, when the latter is weakened, the wire I8 will prevent a separation. At the same time the Wire I8 should be of such gauge that when the section I5 fuses the heat generated will also fuse the wire I8. For fuses of relatively large capacity the Wire I8 may be in one continuous piece from the sleeve I6 to the terminal I1 but, for the lighter capacity fuses where the current capacity of the wire I8 would be substantial in. relation to the rated capacity of the fusible section I5, it is desirable to make the wire I8 in two sections with an insulator I9, of fiber or other suitable material, forming a connection therebetween.

When the fuse link is used in a fuse of the type disclosed in my prior Patent 1,605,543, a current, in excess of the calibrated capacity of the fusible section I5, will fuse the latter first and then the fusible sections I3 and I4, and the gases generated will expel the sections of the link from the tube and also destroy the arcs that are formed. On account of the conductor sections II and I2 not being of sufiicient length to span the distance between adjacent conductors or between any conductor and a ground, there will be no liability for these sections to form a short-circuit and, because the sections are of relatively small mass, they are not liable to seriously injure any apparatus or an attendant, when expelled from the fuse tube.

When the fuse link is used with the form of fuse disclosed in my copending application Serial No. 237,842, filed October 31, 1938, it would be normally under tension, so that a momentary overload which would tend to weaken the fusible section I5 without actually fusing'it, might result in ay rupturing of the fusible section by the tension force to which the link is subjected and the reenforcing wire I8 wouldthen come into play and prevent the rupturing of the fusible section I5 so that the circuit would not, under such circumstances, be interrupted by the momentary overload. However, if the overload is sufficient to fuse the fusible section I5, then the arc that is thereby formed would also fuse the Wire I8 and permit the fuse to function in the usual way. In cases where the overload might fuse the section I5 but be insufficient either in intensity or duration to fuse the fusible sections I3 and I4, the

heat of the gases generated in the fusion of the section I5 would cause the fusion of the sections I3 and I4 and thus permit the link to be expelled from the fuse tube in short sections,

While I have illustrated and described what I now consider to be the preferred embodiment of my invention, it will be understood that various changes may be made in the details of construction without departing from the spirit of the invention as defined in the appended claims. n

Having thus described my invention, I claim:

1. A fuse comprising a plurality of flexible conductor sections fusible at a relatively high temperature and joined together in series by a tubular fusible section that is fusible at a relatively low temperature, and a fusible end section joined to the end of one of said conductor sections and calibrated to be fused by a current of predetermined amperage in a shorter time than the first mentioned fusible section.

2. A fuse comprising at least three flexible conductor sections fusible at a relatively high temperature and joined together in series by tubular fusible sections that are fusible at a relatively low temperature, and a fusible end section joined to the end of one of said conductor sections and calibrated to be fused by a current of predetermined amperage in advance of the fusing of the rst mentioned fusible sections.

3. A fuse comprising at least three exible conductor sections fusible at a relatively high temperature and joined together in series by tubular fusible sections that are fusible at a relatively low temperature, a fusible end section joined to the end of one of said conductor sections and calibrated to be fused by a current of predetermined amperage in advance of the fusing of the rst mentioned fusible sections, a connecting terminal on said end section, and a tension member connecting said terminal with the last mentioned conductor section and reenforcing said fusible end section, said tension member comprising two conductors that are fusible by a current of lower amperage than said predetermined amperage and mechanically connected together by an insulating member.

LESTER. C. HART.

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